Process for the production of alpha-hydroxy amides



:massa Patented Jem. 19, 1965 United States Patent Otiiice 3,166,588 PROCESS FOR THE PRODUCTION OF `QL-HYDROXY AMIDES Herbert E. Johnson, South Charleston, W. Va.,fassignor t; Union Carbide Corporation, a corporation of New ork No Drawing# Filed Apr. 14, 1961, Ser. No.'102,963

. 1 Claim. V(Cl. 260-7-559) Rl OR` i [Batam] (intermediate imido ester) v wherein each R1 individuallyrepresents an alkyl radical having from 1 12 carbon atoms, anA alkenyl radical having from 3-12 carbonatoms o`r an aromatic radical, R2 represents R1 and! hydrogen, and X representsbromine, chlorine and iodine.v 1 f i Illustrative of'thecyanohydrins which can be employed in thenovelprocess of this invention one can include isobutyraldehyde cyanohydrin, acetaldehyde cyanohydrin, alpha methylbutyraldehyde cyanohydrin, phenylacetaldehyde cyanohydrin, 4propionaldehyde cyanohydrin, acetone cyanohydrin, acetophenone cyanohydrin, cyclohexanone cyanohydrin, methylethyl ketone cyanohydrin, acroleincyanohydrin, etc.

`The cyanohydrins which `are used as `starting materials inl the process of this invention are` well known in the art and can) be prepared by various methods. One con- VenientSmet'hOd of preparing them is by reacting an aldehydeor a ketone with 'hydrocyanic acid. This method can beiV represented Aby the followingreaction scheme y wherein R1 and R2 have the s ame meaning -as previously set forth. Y

The alcohols which are operablein the novel process In contrastto the prior art processes, the instant process is conducted in an anhydrous medium so that the alpha-hydroxy amides formed can be easily isolated by conventional means such 'as-'filtration or by direct distillation from the reaction mixture. Additionally, the absence of water excludes the possibility of further reaction of the alpha-hydroxy amides to the correspond.

ing hydroxy acids.

Accordingly, it is the primary object of this invention to provide a process for the production of alpha-hydroxy amides which is convenient, economical and allows for easy` vseparationof the desired product from the reaction mixture.

As has been previously mentioned,'the instantprocess involves the reaction of 1a cyanohydrin with yan alcohol and a hydrogen halide under substantially anhydrous conditions.` The process Acan be carried out by placing tion.

the cyanohydrin and alcohol'in a reaction vessel, bubbling in a hydrogen halide until an intermediate ester is formed, and then pyrolyzing this ester and distilling to yield the alpha-hydroxy amide.` Y

The amount Vof hydrogen halide employed is, not nar-V rowly critical and can vary over a wide range., However, it is preferred to use an excess of` hydrogen halide to cyanohydrin since it insures completion of the reac- Molar ratios of hydrogen halide to the cyanohydrin of 1:1 and lower to 50:1 and higher are operable.

However, vforhpractical considerations, the preferred amount of hydrogen halide employed `in the novel process of this invention is that amountxwhich will completely saturate the alcohol employed or, if a solvent is employed in addition tothe alcohol, that amount which will completely-saturate the solvent.

The amount of lalcohol employed can also vary over a Wide range. However, the use of an excess of alcohol to the cyanohydrin may result in the formation of substantial amounts of ortho or carboxylic ester intermediates which reduces the overall eciency of the process. Thus, although a molarratio o f alcohol to cyanohydrin of from 1:1 and lower to 50:1 and higher can be employed, it is preferred to operate with a ratio of 0.5:1 to 1:1. y

. The temperature atwhich the mixture of alcohol and. cyanohydrin is kept while the hydrogen'halide is added, is also'not narrowly critical. Temperatures within the range of 0v and lower to 50 C. and higher are operable.

The preferredrange is 0` to 25 C. It is also desirable,

though not necessary, to let the reaction mixture standY for a period of time before pyrolyzing the intermediate ester. This length of time can be as much as 48 hours although 4-20` hours will suce. This standing period results in improved yields of the desired alpha-hydroxy of this invention include any Vprimaryor secondary alalcohols, etc.

The `instantiprocess for the production of alphahydroxy l amides possess many desirableadvantages over the prior art methods, The said prior methods usually involved the hydrolysis ofr cyanohydrins .with variousV aqueous amides. The 'preferred hydrogen halide is hydrogen chloride although hydrogen bromide and hydrogen iodide are also operable;

The temperature atwhich the pyrolysis of the intermediate ester takes place is obviously dependent on Vthe particular cyanohydrin and'lalcohol employed. However, these temperatures are usually60 to" 200 C.

In the preferred embodiment of this invention,` the reaction is conducted in the presence of an inert, solvent.

` The use of a solvent eliminates thenecessity of having acids. These processes were notsatisfactory since the v alphahydroxy amides tend to. .beV Avery water soluble which makes their isolation from the reaction mixture verydifcult.l Additionally since the priorart methodsV a pyrolysis step to obtain the desired alpha-hydroxy amide. When a solvent is employed, the reaction lmix` ture is merely reuxed for a period of `time and amide is recovered by filtering the reaction mixture. The reilux period can vary over awide range of from 1 to `l0 hours. The preferred time is from about 4 to 6 hours. It is to be understood that the product can be further purified by conventional meansjsuch as recrystallization.`

The particular,l solvent employed` is 'not critical andr any solvent which is inert to the reaction and boils within the range of about 68 to 200 C. at 760 mm. of mercury, can be used. Illustrative of solvents which are operable include benzene, xylene, dioxane, diisopropyl ether, toluene, etc. The preferred solvent is xylene.

Alpha-hydroxy amides are old in the art and have been used in a wide variety of applications and most recently as substitutes for the corresponding Z-amino acids.

The following examples will illustrate the novel process of this invention.

EXAMPLE 1 A I pmhydroxysovaleramd e A solution of 50 grams of isobutyraldehyde cyanohydrin and 24 grams of ethanol in` 250 ml. of benzene was saturated with dry hydrogen chloride (32 grams) at 25 C. The mixture was then heated slowly to reflux temperature and relluxed 6.5 hours. Upon cooling the product precipitated and was collected to give 38 grams of colorless crystals, M.P. 99-l02 C. Reported M.P. 104 C.

EXAMPLE 2 Example l was repeated except that the reaction mixture was allowed to stand 16 hours at 25 C. before reuxing for four hours. This experiment resulted in 57 grams of product.

EXAMPLE 3 a-Hydroxysovaleramde A solution of 50 grams of isobutyraldehyde cyanohydrin and 46 grams of ethanol in 300 ml. of dry isopropyl ether was saturated with dry hydrogen chloride (76 grams at 25 C.). lThe mixture was then heated slowly to reux temperature and refluxed for 1 hour. Upon cooling the mixture, 66 grams of colorless crystals were obtained, M.P. U-101 C. The infrared spectrum of this material indicates contamination with the intermediate imido ester hydrochloride.

EXAMPLE 4 a-Hydroxyisovaleramide A mixture of 50 grams of isobutyraldehyde cyanohydrin, 27.6 grams of ethanol, 500 ml. of dioxane and 177 grams of hydrogen chloride was prepared and allowed to stand at 25 C. for 18 hours. The mixture was then reluxed for 2 hours, filtered while hot to remove ammonium chloride and then cooled. The precipitated crystals were collected to give 32 grams of impure amide, M.P. 74-77" C.

EXAMPLE 5 a-Hydroxysovaleramde A solution of 50 grams of isobutyraldehyde cyanohydrin in 300 ml. of isopropanol was saturated with hydrogen chloride at 25 C. The mixture was stirred at 25 C. for 18 hours and then reuxed for 8 hours. After iltering the mixture to remove a small amount of ammonium chloride, the isopropanol was removed by distillation under reduced pressure. The remaining residue would not crystallize and is presumed to be, at least in part, the imido ester hydrochloride. Distillation of this material afforded, after pyrolysis of the ester, 43 grams of the desired product, B.P. 14l-148 C. (2.5 mm. Hg). Substitution of sec-butanol for isopropanol gave 43 grams of product, B.P. 13C-142 C. (1.5 mm. Hg)` and the use of 35 grams of allyl alcohol and 250 ml. of isopropanol also afforded43 grams of product, B.P. 127-138 C. (1.0 mm. Hg).

EXAMPLE 6 a-Hydroxyproponmnide chloride at 30 C., the temperature being very diicult to control. After several hours the imido ester crystallized from the reaction mixture. The mixture was allowed to stand at 25 C. for 16 hours and then heated under reduced pressure. When the pyrolysis was complete grams of the desired amide distilled at l64-175 C. (5.0 mm. Hg), M.P. 63-65 C. A purified sample melted at 74-75 C. Reported M.P. 74 C.

EXAMPLE 7 a-Hydroxy--methylvaleramde A mixture of 57 grams of alpha-methylbutyraldehyde cyanohydrin, 35 grams of allyl alcohol, 250 ml. of benzene and 3l grams of hydrogen chloride was prepared and allowed to stand at 25 C. for 20 hours. After reuxing the mixture for 4 hours it was ltered to remove a trace of solids and evaporated under reduced pressure. The remaining residue was distilled, B.P. 136-154 C; `(1.5-3 mm. Hg) to give 49 grams of product that slowly solidihed. Repeated crystallizationl of a sample of this lmaterial from isopropyl ether gave an analytical sample as colorless prisms, M.P. 49-56 C.

ANALYSIS FOR CuI-IiaNOa C H I N Calculated 54.94 9 99 10. 6s Found 55.16 10. 03 10. 63

EXAMPLE 8 1t-Hydroxy--phenylproponamde A mixture of 74 grams of phenylacetaldehyde cyanohydrin, 24 grams of ethanol, 300 ml. of dry benzene and 44 grams of hydrogen chloride was prepared and, after standing at 25 C. for 18 hours, relluxed for 5 hours. Upon cooling the mixture, 68 grams of product precipitated as colorless crystals, M.P. -1l3 C. Reported M.P. is lll-112 C.

EPQMPLE 9 a-Hydroxybutyramde A solution of 170 grams of propionaldehydeV cyanohydrin and grams of isopropanol in 1.5 l. of xylene was saturated at 25 C. with hydrogen chloride. The mixture was kept for about 50 hours at 25 C. and then reuxed for 7 hours. Cooling the mixture precipitated 179 grams of light yellow solids, M.P. 76-89 C. An analytical sample, M.P. 104-108 C. was prepared by crystallization from benzene-ethanol.

ANALYSIS FOR C4HoN0a hydrin, 8.5 grams of ethanol and 200 ml. of toluene was saturated with hydrogen chloride at v25 C. The reaction mixture was kept at 25 C.'for about 50 hours and then reuxed for 2 hours. After a filtration to remove a small amount of ammonium chloride the toluene was removed by evaporation under reduced pressure. The remaining liquid was distilled to give 13.8 grams of a viscous liquid,` B.P. 11G-130 C. (3.5 mm. Hg) that slowly solidified, M.P. 59-'766 C. An analytical sample was obtained by-` crystallization from chloroform, M.P. r67.5-69 C.V Y

5 ANALYSIS FOR CGHnNOn o H N Calculated 51.26 9.46 11.95 Found 51.55 9.69 11.94

matic hydrocarbon; and R2 is of the group consisting of hydrogen, alkyl of 1 to 12 carbons, alkenyl of 3 to 12 Y carbons and aromatic hydrocarbon.

References Cited in the le of this patent UNTED STATES PATENTS 2,229,897 Migrdichian Ian. 28, 1941 2,457,660 Gresharnet al 'Dec. 28, 1948 2,573,673l Ritter Oct. 30, 1951 2,601,387 Gresham et al lune 24, 1952 2,632,766 De Benneville Mar. 24, 1953 2,719,176 Coover et al. Sept. 27, 1955 OTHER REFERENCES Plant et al.: ourn. Amer. Chem. Soo, Vol. 73, pp. 4076-77 (1951). Y

Mackenzie et al.: Jour. Org. Chem., Vol. 1S, pp. 594- 7 (1953), QD 24136.

Felkin Comptes Rendus, Vol. 240, pp. 2322-4 (1955), Q 46A14. Y

Morgan Chem. and Ind., pp. 854-855 (April-June, 1959), TP 1 S 63. 

